The present invention relates to radiometry and, more particularly, to a terahertz radiation liquid crystal imaging system.
Over the past 30 years, thermochromic liquid crystal (TLC)-based thermography systems have provided engineers with a relatively inexpensive technique for investigating thermal phenomena in the electronics, automotive, and aerospace industries, as well as in academia.
Conventional TLC thermal imaging devices include an infra-red sensitive detector and one or more infra-red optical components which focus the radiation from a thermal scene on to the surface of the detector, which operates to convert the infra-red radiation into visible radiation. The material of the detector (converter) is chosen to have a highly temperature-dependent optical property, such as birefringence or optical rotation. This detector is also illuminated by a visible or near-visible polarized light source the output of which is reflected onto the detector. The visible or near-visible light experiences a modulation of polarization, on passing through the detector, which is converted to an intensity modulation by a quarter-wave plate and an analyzer. This intensity modulation conferred on the light passing through the detector thus corresponds to temperature variations induced in the detector by the infra-red radiation. In conventional devices, the modulated light is then focused by lenses through a Fourier plane filter on to a television camera chip the output of which is read into a frame store.
In order to vary the field of view of the device, an infra-red zoom lens is used to focus the radiation from the thermal scene on to the liquid crystal. Infra-red lenses are expensive, and infra-red zoom lenses particularly so; so for any individual system, the range of lenses is usually limited.
However, shortcomings still remain. The lack of sensitivity of the detector to non-visible radiation is still a problem that confronts the art. Accordingly, there is a need in the art for a method and device that will improve sensitivity of thermal imaging devices.